Recently, in order to reduce air pollution caused by an exhaust gas of vehicles, a vehicle is manufactured based on the study for ensuring a driving force with an internal combustion engine and/or an electric motor. Accordingly, the vehicle has evolved in the order of a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle. In this case, the hybrid vehicle and the plug-in hybrid vehicle include an internal combustion engine, an electric motor and a battery pack, and the electric vehicle includes an electric motor and a battery pack without an internal combustion engine.
In addition, the battery pack has also evolved along with the hybrid vehicle, the plug-in hybrid vehicle and the electric vehicle. The battery pack is configured to be charged in and/or out of the electric vehicle. The battery pack has a battery laminate surrounded by a lower housing and an upper housing and composed of secondary batteries included therein. Here, the lower housing has at least one electric terminal electrically connected to the battery laminate. The electric terminal is surrounded by a rubber sealing and inserted into a through hole of the upper housing to protrude from the upper housing.
In this case, if the rubber sealing is badly deformed elastically between the lower housing and the upper housing, the rubber sealing partially opens a space between the upper housing and the electric terminal. The bad elastic deformation of the rubber sealing allows water to penetrate toward the through hole of the upper housing from the outside of the upper housing. The penetration of water forms a water flow path along the electric terminal toward the inside of the battery pack and causes an electric short among components in the battery pack.
Therefore, various studies have been made in order to prevent an electric short among components in the battery pack, caused by the penetration of water. Among the studies, there is Japanese Unexamined Patent Publication H10-69893 (published on Mar. 10, 1998), entitled “a pack battery having an electrode window with a water proof structure”. The pack battery includes a rubber sponge and a terminal holder between a lower case and an upper case. The rubber sponge is located on the terminal holder, and the terminal holder has a convex electrode portion surrounded by the rubber sponge.
The convex electrode portion is covered with an electrode terminal at its upper side and inserted into the electrode window of the upper case. The rubber sponge is stably pressed by the upper case at the inside of the pack battery to make elastic deformation, thereby shielding a space between the electrode window and the convex terminal portion. However, if the rubber sponge is aged during the service life of the battery pack, the rubber sponge is hardened in comparison to a time when it is initially mounted to the convex terminal portion, thereby being easily worn out or corroded due to a friction with peripheral components.
The wear and corrosion of the rubber sponge results in imperfect shielding of the space between the upper case and the convex terminal portion through the electrode window of the upper case. In this way, if the rubber sponge is aged, water may penetrate toward the electrode window of the upper case from the outside of the upper case.